// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CONTENT_BROWSER_DOWNLOAD_RATE_ESTIMATOR_H_
#define CONTENT_BROWSER_DOWNLOAD_RATE_ESTIMATOR_H_

#include <stddef.h>
#include <stdint.h>

#include <string>
#include <vector>

#include "base/time/time.h"
#include "content/common/content_export.h"

namespace content {

// RateEstimator generates rate estimates based on recent activity.
//
// Internally it uses a fixed-size ring buffer, and develops estimates
// based on a small sliding window of activity.
class CONTENT_EXPORT RateEstimator {
public:
    RateEstimator();
    RateEstimator(base::TimeDelta bucket_time,
        size_t num_buckets,
        base::TimeTicks now);
    ~RateEstimator();

    // Increment the counter by |count|. The first variant uses the current time,
    // the second variant provides the time that |count| is observed.
    void Increment(uint32_t count);
    void Increment(uint32_t count, base::TimeTicks now);

    // Get a rate estimate, in terms of counts/second. The first variant uses the
    // current time, the second variant provides the time.
    uint64_t GetCountPerSecond() const;
    uint64_t GetCountPerSecond(base::TimeTicks now) const;

private:
    void ClearOldBuckets(base::TimeTicks now);
    void ResetBuckets(base::TimeTicks now);

    std::vector<uint32_t> history_;
    base::TimeDelta bucket_time_;
    size_t oldest_index_;
    size_t bucket_count_;
    base::TimeTicks oldest_time_;
};

} // namespace content

#endif // CONTENT_BROWSER_DOWNLOAD_RATE_ESTIMATOR_H_
